That last page has "HOME" selected, so I assumed that was the homepage at Codeplex I was looking at. I had no way of knowing that wasn't it, especially with the lack of navigation. So, here's my suggestions:

Put a link to the changelog on the Downloads page

Link to the Codeplex homepage from idrix.fr

Link to the Codeplex homepage from the program's About screen

Call the page "Release notes / Changelog" so a search for "changelog" will pick it up.